Hazardous or toxic waste destruction or containment – Containment – Solidification – vitrification – or cementation
Reexamination Certificate
2000-06-23
2003-05-27
Silverman, Stanley S. (Department: 1754)
Hazardous or toxic waste destruction or containment
Containment
Solidification, vitrification, or cementation
C588S253000
Reexamination Certificate
active
06570048
ABSTRACT:
This invention is in the field of chemical processes; more specifically, this invention relates to methods for oxidizing organic compounds whose molecular structures include at least one carbon-phosphorous bond. The process is especially useful in the oxidation of organic phosphinates to inorganic orthophosphates.
BACKGROUND OF THE INVENTION
In a broad sense, organophosphorous compounds contain at least one phosphorous atom chemically bonded directly or indirectly to a carbon skeleton. The phosphorous atom may be a member of an organic chain or ring system in which phosphorous is bonded directly to carbon, or phosphorous may be the central atom in a functional group which in turn is bonded to a carbon-containing chain or ring. Such functional groups commonly have one or more oxygen atoms or hydroxyl (—OH) groups surrounding the phosphorous atom.
Examples of organophosphorous compounds in which phosphorous is bonded directly to carbon include: phosphines R
3
P, phosphine oxides R
3
PO, phosphonic acids RP(O)(OH)
2
, phosphonous acids RPH(O)(OH), phosphinous acids R
2
POH, phosphoranes R
3
P═CH
2
, and biphosphines R
2
P—PR
2
. Examples of organophosphorous compounds in which phosphorous is bonded both directly and indirectly to carbon include phosphonates RP(O)(OR′)
2
, phosphonites RPH(O)(OR′), phosphinites R
2
P(OR′), phosphonamides RP(O)(NR′R″)
2
, and phosphinamides R
2
P(NR′). The alkyl phosphonates and phosphinates are related to phosphonic acid HP(O)(OH)
2
and phosphinic acid H
2
P(O)OH, respectively. In all of these examples the R, R′ and R″ moieties can be the same or different and any combination of alkyl or aromatic groups. Further examples of the large number of these compounds can be found in the seminal textbook “Organophosphorous Compounds” by G. Kosolapoff, John Wiley and Sons, New York, N.Y., 1950.
The organophosphorous compounds within the scope of this invention all contain phosphorous directly bonded to carbon. The compounds additionally may include phosphorous indirectly connected to carbon, but the structural feature of the organophosphorous compounds central to the process of this invention is:
P—C (I)
Although the process of this invention is of general utility, it is especially useful when applied to organophosphorous compounds represented generally by chemical structure II:
The compounds of formula II are called “phosphinates.”
Within the set of the phosphinates of structure II is a subset, a number of which are chemical warfare agents; more specifically, the subset includes some extremely toxic cholinesterase inhibitors, i.e., nerve agents. This subset is included in the compounds represented by formula III:
in which R
1
is selected from hydrogen and alkyl, R
2
is independently selected from alkyl, and Y is a leaving group.
Destruction of chemical warfare agents, including nerve agents within the scope of formula III, is the subject of PCT Application WO 97/18858, published May 29, 1997 and counterpart U.S. Pat. 5,598,691, dated Dec. 7, 1999, either or both of which are referred to as “the earlier patent” hereinafter and are incorporated herein by reference. Included in the disclosure of the earlier patent is a preferred process for destroying chemical warfare agents by subjecting them to a “dissolving metal reduction.” The reduction involves creating a reaction mixture prepared from raw materials which include nitrogenous base, e.g., anhydrous liquid ammonia, at least one chemical warfare agent, e.g., a nerve agent of formula III, and an active metal, such as sodium. The dissolving metal reaction generates solvated electrons, a highly active reducing agent. The reduction reaction results in a product which includes, among other substances, the phosphinate salts represented by formula IV:
in which R
1
and R
2
are the same as in formula III, and Z is a cation of charge n. Noteworthy is the fact that the salts of formula IV still contain phosphorous-carbon bonds P—R
2
.
The earlier patent suggests oxidation of the product from reduction of the chemical warfare agent in order to simplify its disposal as waste. However, the suggested oxidation with agents, such as hydrogen peroxide may leave some of the P—R
2
phosphorous-carbon bonds intact. The continued presence of phosphorous-carbon bonds raises toxicity issues and presents additional waste disposal problems.
SUMMARY OF THE INVENTION
Thus, it would be beneficial to provide a method for breaking the carbon-phosphorous bonds found in the organophosphorous compounds of the aforesaid formulae in order to provide a new synthetic route to useful materials and also to reduce the toxicity of the organophosphorous compounds of the aforesaid formulae and render them more environmentally acceptable.
Therefore, it is an objective of this invention to provide a method for attaining these ends starting with organophosphorous compounds having the structural feature of formula I. It is another objective to provide a process which is especially applicable to break the carbon-phosphorous bonds in organophosphorous compounds within the scope of formula II. Yet another objective is to provide a unique method for destroying, i.e, breaking the carbon-phosphorous bond in the phosphinates of formula III, including destruction of those compounds of formula III which are chemical warfare agents. It is still another objective to provide a method for oxidizing compounds of formula IV, especially as a follow-up to the dissolving metal reduction of the chemical warfare agents within the scope of formula III, thereby decreasing the toxicity of the reduction products and simplifying their disposal as waste.
Accordingly, in attaining the aforesaid objectives this invention provides a process for converting organophosphorous compounds of formulae II, III, and IV, all of which contain the structural feature of formula I, into relatively benign organic compounds and inorganic salts which often are soluble in water and are relatively safe, environmentally.
In order to accomplish these objectives, it is preferred to treat the organophosphorous compounds with an oxidizing agent comprising a peroxysulfate of formula V,
M
2
S
x
O
y
(V)
in which M is a monovalent cation, x is 1 or 2, y is 5 when x is 1, and y is 8 when x is 2; M
2
SO
5
is a peroxymonosulfate, while M
2
S
2
O
8
is a peroxydisulfate. The process is preferably carried out in the presence of water, and in addition, should be conducted in an alkaline pH range. This is in contrast to the methods of John F. Cooper, et al, described in a paper entitled “Destruction of VX by Aqueous-Phase Oxidation Using Peroxydisulfate (Direct Chemical Oxidation)” presented at the Workshop on Advances in Alternative Demilitarization Technologies, Reston, Va., Sep. 25-27, 1995. The oxidation processes of Cooper et al were carried out using acidified ammonium peroxydisufate with pHs adjusted down to 1.5. Unlike the methods of Cooper et al, these inventors found that although some reaction occurs in the acid pH range, cleavage of the carbon-phosphorus bond is greatly facilitated when performed under alkaline conditions, i.e., pH>7, and at elevated temperatures. The addition of base, such as sodium hydroxide also allows lesser amounts of the peroxysulfate to be used, making it more economic.
The chemistry of peroxysulfate oxidation/reduction, including kinetics and mechanism, has been described in I. M. Kolthoff and I. K. Miller,
J. Am. Chem. Soc
., 73, 3055 (1951) and in L. S. Levitt,
Can. J. Chem
., 31, 918 (1963). The oxidation of methylphosphonic acid, CH
3
P(O)(OH)
2
, using ozone/oxygen at pH 8-8.5 in aqueous sodium bicarbonate to yield phosphoric acid has been reported; see V. V. Smirnov, et al.,
Zh. Obshch. Khim
., 37(12) 2783-4 (1967); C.A. 68:113762x. Related disclosures are found in
Zh. Obshch. Khim
., 38(5) 1197 (1968); C.A. 69 77373f and
Zh. Obshch. Khim
., 39(4) 932 (1969); C.A. 71 56020q. The oxidation with aqueous HNO
3
/KMnO
4
of a series of compounds RPO
3
H
2
in which R is alkyl is de
Getman Gerry D.
Hunter Wood E.
Moyer Rudolph H.
Commodore Applied Technologies, Inc.
Ellis Howard M.
Kuhar Anthony
Silverman Stanley S.
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